The present invention relates to a self-diagnosis system for detecting faults in a transceiver within a wireless receiving unit of a base transceiver station. More specifically, the present invention relates to a self-diagnostic method for diagnosing and detecting faults in an internal circuit of the transceiver unit in a radio base transceiver system (BTS) and an apparatus thereof.
In a mobile communication system, namely, in a conventional code division multiple access (CDMA) system, the system is provided with a plurality of mobile stations, a plurality of base transceiver systems (BTSs) for providing communication service to the mobile stations, a base station controller (BSC) for connecting the BTSs with a mobile switching center (MSC), and the MSC for connecting the BSC to a public switched telephone network (PSTN).
FIG. 1 is a block diagram which illustrates a radio frequency (RF) receive path of a typical CDMA cellular BTS. The BTS includes an out-door system 1 for receiving a radio frequency (RF) signal from mobile stations, and an in-door system 2 for processing the received signal.
The in-door system 2 includes a RF unit (RFU) 3 for converting the received RF signal into an intermediate frequency (IF), a digital unit (DU) 4 for demodulating the RFU transmitted signal into a digital signal, and a base station test unit (BTU) 5 coupled to the RFU for testing the BTS.
The RFU 3 includes a front-end unit (REU) 3a coupled to a receiving antenna, a transceiver unit (XCVU) 3b for down converting the received signal into an IF and for outputting the IF at a regular level, and an IF amplifier/divider 3c for transmitting the converted IF signal to the digital unit (DU) 4.
The digital unit (DU) 4 includes a digital signaling unit 4a for demodulating the received signal from the IF amplifier/divider 3c. The BTU 5 includes a RF switch 5a coupled to the front-end unit (FEU) 3a, a variable attenuator 5b for regulating an attenuation value of the signal which is transmitted to the RF switch 5a, and a test mobile (TM) 5c, coupled to the variable attenuator 5b, for providing a test signal.
In the above base transceiver system of a mobile communication system, the base station test unit (BTU) 5 is used to detect for any fault in the receive path when the fault occurs.
FIG. 2 is a flow chart which illustrates a prior method for checking a fault of a receive path of a BTS. In the prior diagnostic method, a fault diagnostic apparatus ascertains a call being currently communicated in a BTS (step 101). If a call were ongoing, the fault diagnosis is terminated since a fault diagnosis can""t be performed during the call being communicated. (step 102). When no call is currently being communicated, the output level of the test unit 5c is properly adjusted and is provided to the transceiver unit 3b via a front-end unit 3a (step 103). The fault diagnosis apparatus remembers the provided output level of the test unit 5c (step 104).
The diagnostic apparatus for detecting faults reads the received input signal level measured by the transceiver unit 3b (step 105), and then compares the received input signal level with the remembered output signal of the test unit 5c (step 106), in order to determine whether the difference of these two signals exceeds a predetermined value of 10 dB (step 107). If the difference exceeds 10 dB, it is determined that a fault exists in the receive path. Thereafter, the diagnosis apparatus reads an IF level outputted from the transceiver unit 3b (step 108) and compares the read IF level with the IF level which was previously saved in an inner memory of the transceiver unit 3b (step 109). If these two compared IF levels are different, it is determined that a fault exists in the transceiver unit 3b (step 110), and if not, it is determined that a fault exists in the front-end unit 3a. 
However, if the difference does not exceed 10 dB in step 106, the diagnostic apparatus ascertains as to whether an alarm is reported in the output of the transceiver unit 3b (step 112). If an alarm is reported, it is determined that a fault exists in the IF amplifier/divider 3c, otherwise, it is determined that no fault exists in the receive path of the BTS and all diagnostic procedures are terminated.
As illustrated in the above, the prior known technique uses a base station test unit (BTU) for checking functions of a RF unit. However, the problem with the prior method is that an extra device, for example a BTU, is required for detecting any fault in the system, and moreover, it takes a long time to detect such fault due to very long and complicated diagnostic method. Also, the prior method is not applicable for detecting faults in an internal circuit of the transceiver unit, but only limited to detect faults in a RF unit.
U.S. Pat. No. 5,640,401 entitled, xe2x80x9cCommunication Circuit Fault Detector,xe2x80x9d discloses a communication detector for testing a communication circuit. The communication circuit fault detector generates a test signal and inputs the test signal to the communication circuit to compare the original test signal with the returned test signal outputted from the communication circuit. However, since such fault detector is directed only to detect for a fault in a typical data communication circuit, it is not possible to detect for a fault in an inner circuit of a transceiver unit of a BTS.
One object of the present invention to provide a self-diagnosis system of a transceiver unit for detecting faults in its internal circuit by measuring an auto gain controller control voltage value and an IF detection voltage value of a down converter, and thereafter by comparing to a reference value.
Other objects and advantages will be more easily understood by the following detailed description and accompanying drawings.
It is another object of the present invention to provide a wireless receiving unit of a base transceiver station comprising a down converter and a transceiver slave control board, wherein the down converter includes an amplifier for amplifying a received signal, an automatic gain controller (AGC) for controlling a signal level of the amplified received signal, an AGC detector for detecting an intermediate frequency (IF) detection voltage value and for determining the AGC control voltage value, a transceiver slave control board, which includes an analog to digital converter for converting the IF detection voltage value from the down converter and for converting the AGC control voltage value into digital value, an EEPROM for storing predetermined reference values, a look up table for converting the AGC control voltage values into the received input signal levels, and a maximum, minimum and average IF detection voltage values responsive to changes of the received input signal.
Another object of the present invention is to provide a self-diagnostic method for detecting faults in a transceiver comprising the steps of reading a predetermined first minimum value of received input signal level and a predetermined first maximum value of received input signal level applied to the wireless receiving unit, reading an instantaneous control voltage value of the AGC, converting the instantaneous control voltage value into a received input signal level in accordance with the look up table, and determining that a fault exists in the amplifier operation of the down converter when the converted received input signal is below the predetermined first minimum value of the received input signal level and determining that a fault exists in the amplifier operation of the down converter when the converted received input signal exceeds the predetermined first maximum value of the received input signal level, reading a predetermined second minimum value of the intermediate frequency (IF) detection voltage value and a predetermined second maximum value of the intermediate frequency (IF) detection voltage value when the converted received input signal level stays between the predetermined first minimum value and the predetermined first maximum value of the received input signal levels, reading an instantaneous IF detection voltage value which is measured by the AGC detector and determining that a fault exists in the AGC operation of the down converter when the instantaneous IF detection voltage value is below the predetermined second minimum value of IF detection voltage value and determining that a fault exists in the AGC operation of the down converter when the instantaneous IF detection voltage value exceeds the predetermined second maximum value of IF detection voltage value.
It is further object of the present invention to provide a self-diagnostic apparatus for detecting faults in a transceiver within a wireless receiving unit of a base transceiver station comprising a down converter having an amplifier for amplifying the received input signal, an automatic gain controller (AGC) for regulating the level of the amplified received input signal, an AGC detector for detecting an instantaneous intermediate frequency (IF) detection voltage value and for determining an instantaneous AGC control voltage value, and a transceiver slave control board having a microprocessor, an analog to digital converter for converting the instantaneous IF detection voltage value and the instantaneous AGC control voltage value into digital values, and a memory device for converting the instantaneous AGC control voltage value into corresponding received input signal level and for storing predetermined reference values and a maximum, minimum and average value of IF signal detection voltage value in accordance with changes of the received input signals, wherein the microprocessor compares the instantaneous AGC control voltage value provided by the down converter with a predetermined first minimum value and a predetermined first maximum value of the received input signal levels, respectively, for determining that a fault exists in the amplifying operation of the down converter when the converted received input signal level of the instantaneous AGC control voltage value is below the predetermined first minimum value of the received input signal level or exceeds the predetermined first maximum value of the received input signal level, and thereafter, if the converted received input signal level stays between the range of the predetermined first minimum value and predetermined first maximum value of the received input signal levels, compares the instantaneous IF detection voltage value provided by the down converter with the predetermined second minimum value and a predetermined second maximum value of the IF detection voltage value, respectively, for determining that the down converter""s AGC operation is faulty when the instantaneous IF detection voltage value is below the second minimum value of the IF detection voltage value or exceeds the predetermined second maximum value of the IF detection voltage value.